package P1400;

import java.util.Scanner;

/**
 * @author: zhouyang
 * @descrpition:
 * @time: 2019-10-07 13:12
 */
public class P1423_小玉在游泳 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double distance = scanner.nextDouble();
        scanner.close();
        int index = 0;
        double sum = 0d;
        double before = 2d;
        while(sum < distance){
            sum += before;
            before *= 0.98;
            ++index;
        }
        System.out.println(index);
    }
}
